ictc
Member
Last Activity: 04-04-2025, 03:15 AM
Joined: 05-07-2015
Location: Roma
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By the way I also was unable to find the UART as suggested in another reply ... -
Yes, I'm sorry for not expressing myself clearly enough. I manually released the tray using the access point under the casing, specifically designed for manual ejection. I had to do that at the beginning in order to remove the front panel. I did it once again just to be sure but it didn't have any effect. Thanks again!...Leave a comment:
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Of course, no signs of life. Also tested the only 2 caps on the motherboard and they tested fine too....Leave a comment:
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do you mean the electrolytic capacitors on the mainboard? I allready checked the SMPS and they are fine so far... the unit still perfectly clean inside perheaps not used very often.Leave a comment:
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update, the client doesn't want it back so I can give a try eventually....Leave a comment:
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Thank you all for your input, though I still have some doubts. No evidence of shorts was found on the ETH and HDMI ports. However, I did notice signs of corrosion on R190 (a large 0-ohm resistor connected to HDMI_VCC) and a small mark on the PCB that made me think a spark might have occurred. You know when, after a spark, the PCB shows a halo with various color gradients, likely due to the evaporation of some metallic oxide? In this case, the phenomenon is almost imperceptible to an untrained or inattentive eye, and I might have overthought it or exaggerated its significance. There's no actual...Leave a comment:
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Philips MDP 3380/12 Blu-ray Player – No Power, Reset Signal Always High
I'm troubleshooting a Philips MDP 3380/12 Blu-ray player that shows no signs of life. The display remains off, and no buttons respond.
Inside, the power supply is working correctly, and all expected voltages on the mainboard match the service manual specifications. The CPU warms up slightly (checked with a thermal camera), the crystal oscillator is functioning, but the reset signal remains high at all times.
The reset circuit appears to consist of two NPN transistors, one driven by 5V VCC and the other by 3.3V STBY, as shown in the attached schematic. Should the reset... -
I managed to desolder the CPU with only a couple of not connected pads ripped off. I found out that the very thin PCB thickness allow an easy and fast desolder compared to other thicker motherboard. The dark glue was not actually a problem. My only problem now is finding the right stencil to reball the CPU. I also caused some solder mask to peel off during desoldering and I need to reapply the green oll entirely without a proper stencil...that would be the most annoying part so far.Leave a comment:
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Has anyone found a more effective yet conservative way to remove this type of glue? I need to attempt a CPU reflow and have already tried at least two different BGA glue solvents without success in softening that gunk. Any advice?Leave a comment:
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I'ma having the same issue with an IdeaPad ryzen 5, I thought could have been the onboard ram failing but that should not explain why after crash the CPU temperature suddenly rise up of about 5 degrees. I also tried replacing the bios with no luck at all. I'll try the reflow and if anything changes in better I'll manage to perform a complete reballing. Do you have experienced other random freeze after reflow?...Leave a comment:
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Lenovo IdeaPad S145 boot when cold than crash after feew minutes
I received this laptop, which initially boots into Windows normally, but after a few minutes, the system freezes with no display and no response except for power button. When this happens, power consumption rises to about 1A (without the battery connected), and the CPU becomes noticeably hotter compared to when the machine is operating normally.
I have already tried removing the additional RAM module, which initially showed some promise, but the issue persisted after a reboot. I also attempted replacing the BIOS, but this did not resolve the problem.
When the system crashes,... -
the resistance value on +3VLP is 32Kohms measured on PC411 with red probe on ground, viceversa I don't get a fixed value.
Considering that PJ403 powers only the circuit of PU401, I decided to reconnect that jumper and open PJ401, which is instead related to +3VALWP. However, at that point, I once again lose the +19VB.Leave a comment:
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To further narrow down the issue, I selectively removed the jumpers connecting the main power rail to various sections of the circuit in order to identify the faulty section responsible for the malfunction, which causes the +19Vb power rail to shut down due to the primary power circuit entering protection mode. This method allowed me to pinpoint the jumper labeled [B]PJ403[/B], associated with the 3V3 generation circuit connected to the [B]PU401[/B].
However, no short circuit was detected at the output of the 3V3 generation circuit. This suggests that the issue might extend to other...Leave a comment:
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Yes, I agree. However, how can I determine what is happening at +19VB that prevents the charging circuitry, which seems to be functioning correctly, from delivering voltage to the rest of the board? If there is no short circuit, what should I check next? The only assumption I can make at this point is that the short might not be on the main rail. However, I haven't been able to identify any shorts on any of the coils.
...Leave a comment:
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still measuring Mohm value on +19VB... Apparently no direct short on this rail but someting get weird when powerd up. Can we exclude problems on PU301 side? Injecting voltage on this rail without a short would it make any sense?Leave a comment:
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I removed PQ304 and measured VCC again... Perfectly stable! Could it be something related to the PQ304 load side? I wondered. The MOSFET has also been replaced with no luck. Without it, the IC seems to function properly, providing the correct gate voltage and showing a perfectly stable VCC.
Next, I tried removing both current sense resistors (PR335 and PR304), and, as expected, I got 19V_P2.
What's still driving me nuts is the 4.27V reading I get on the +19VB side...
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with PR312 in place, negative probe on ground positive on vcc ..6.85Mohm, reversing probes 0.5Mohm. Without PR312 negative probe on ground 8.3Mohm, reverse 1.94Mohm
PC314 not shorted
PQ302 seems to be ok no low resistance in any probing combination.
No low impedance on any of the pin of PU301...Leave a comment:
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Diode replaced from a doner board, voltage now around 2044 but some times rised up till 20.7 than stabilized around 20.6. resoldered the 10ohm resistor in place and measured VCC... same identical situation as before... Could it be that the IC is struggling to manage the output of the second MOSFET, perhaps due to a varying demand for current from Vcc? It might be that, for some reason, it shuts down and then immediately attempts to restart, only to encounter the same conditions forcing it to vary its current draw again. This could create a sort of loop, which would then manifest as fluctuating...Leave a comment:
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Not at all. +19V_VIN is 19.5V as it should be, but the output of the dual diode is still not stable, fluctuating sometimes between 20.7V and 22.9V. I also noticed that on the +19VB pin of the same diode, the voltage is sometimes 0V and other times randomly varies between 2.3V and 5V.
When the adapter is connected for the first time, I have approximately no +19VB and an almost steady 20.6V on +19V_VIN. After a while, +19VB starts increasing, and +19V_VIN begins to fluctuate as well. However, these two events don't appear to be directly correlated, as at the moment, I have 20.5V on...Leave a comment:
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Removed PR312 and measured the resistance to ground. From diode PD301 side it is 2.9M and on the IC PU301 side is 1.7M. The dual diode also seems fine to me, about 0,28V of voltage drop in diode mode on both diode.Leave a comment:
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